Add scripts/export_targets.py. $ export_targets.py <out_dir> <targets...> Flattens all library targets under <targets...> and checks that all includes in 'sources' are known to the build. Firefox can use this as the first half of our ANGLE vendoring process. Included additions to src/libGLESv2.gni were found with: $ export_targets.py out //:libEGL Eventually, it would be nice to have this as a presubmit check. Bug: angleproject:3403 Change-Id: I0f455e8c37c4b0a9e17e9f843843422b6a32f588 Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/1584652 Commit-Queue: Kenneth Russell <kbr@chromium.org> Reviewed-by: Geoff Lang <geofflang@chromium.org> Reviewed-by: Kenneth Russell <kbr@chromium.org>